This invention concerns the production of uniform dimensioned particles, and more particularly, novel apparatus and methodology for producing uniform dimensioned spheres of minute sizes from various materials by forming uniform droplets containing uniform amounts of the materials and a uniform amount of a sheath liquid and a uniform amount of a core liquid immiscible with the sheath liquid.
Minute, spherical particles which are very uniform in volume and which can contain a uniform amount of an added material, such as a dye, have utility in many fields. For example, uniform plastic particles having known and controllable physical and optical properties are of great aid in developing instruments for use in biological cell analysis. The particles are highly useful also in the testing and calibration of such instruments. Particles of uranium oxide and plutonium oxide having uniform volume provide useful reactor fuel materials. Microspheres of radioactive materials that are uniform in size and volume are highly desirable for use in many biological and medical studies including those concerning deposition of various sizes of blood borne particles in the lungs, distribution of fetal blood flow, and distribution of cardiac output, for instance.
A uniform particle formed within a particle could be used in light scatter or other cell studies where a difference in the index of refraction between the cytoplasm and the nucleus is important. By forming a particle within a particle or a particle within a particle within a particle, very uniform pseudo-cells can be formed for calibrating and developing instruments used in these studies.
One system for producing uniform particles is shown in Fulwyler M. J., U.S. Pat. No. 3,790,492, issued Feb. 5, 1974. In this system, droplets of core liquid are formed in a laminar, flowing stream of sheath liquid. In utilizing this system it has been found that a small orifice, on the order of 20 microns in diameter, must be used to inject the core liquid into the moving stream of sheath liquid. Because of its small size, the nozzle used in this system is subject to plugging by the core liquid. Another limitation found in utilizing this system, is that the core liquid must be injected into the moving stream of sheath liquid essentially at the relatively low velocity of the sheath liquid to prevent the occurrence of turbulence. This results in a limited rate of droplet production on the order of 13,000 droplets per second. The size range of the diameters of the particles produced by this system is on the order of, but not limited to, 2 to 40 microns.